Compression release



R. M. HVID.

COMPRESSIQN RELEASE. APPLlcAvTloN man No.3, 1917.

PatentedA Nov. 5,1918.

2 SHEETS SHEET l.

R. M. HVID.

GOMPRESSION RELEASE.

APPLICATION FILED DEC.3. 1917.

1 ,283,780. Patented Nov; 5, 1918.

2 SHEETS-SHEET 2.

` QQQQQQQQQQ Patented Mar'. 7, 1944 UNITED STATES PATENT OFFICE REACTIONBETWEEN SOLIDS AND GASES Warren K. Lewis, Cambridge, Mass., assignor toStandard Gil Development Company, a corporation of Delaware ApplicationAugust l, 1941, Serial No. 405,033

' (ci. vs -2s) Claims.

The present invention is directed to chemical reactions between solidsand gases and particularly to the recovery of metals from their ores,such as iron from iron ore, nickel from nickel ore, etc.

In the past efforts have been madeto utilize natural gas for therecovery of iron from iron ore. Many attempts have met with failurebecause the procedure adopted was to utilize the natural gas directly asa. source of heat and as a reducing agent. Natural gas is an inefllcientreducing agent and the result of the aforesaid attempts has been theconclusion that natural gas offers little promise as a substitute forsolid fuel in the smelting of iron ore.

According to the present invention natural gas is utilized in thesmelting of iron ore by ilrst subjecting it to a treatment capable ofconverting it intoa gas rich in free hydrogen and then utilizing vthisgas in a unique manner for the reduction of iron ore. This latter stepis accomplished laccording to the present invention by suspendingpowdered iron ore in a stream of the gas in such -a way that the mixturepresents the appearance of a boiling liquid and the powdered iron oreand resulting powdered iron is carried along slowly in the gas stream.This has been achieved by regulation of the gas velocity. To put itanother way, a substantially uniform dispersion of powdered iron andiron ore is carried along in a stream of the gas at a rate lower thanthe velocity of the gas stream. In order that this may be achieved thisreduction step is conducted at a temperature below the plastictemperature of metallic iron. A suitable temperature is intheneighborhoid of 700 C., the minimum temperature being dictated by thatnecessary to support the reaction between hydrogen and iron oxide.

In practice, it is preferred to subject the nat ural gas to pyrolysistoconvert it into carbon and hydrogen because in thisv case the carbonproduced is thermatomic carbon, which lends ,itself readily tointroduction into a flowing streainof the powdered iron forcarburization of the latter. If desired, however, the natural gas may bereacted with steam in the 'presence of a catalyst-under conditionsfavorable to the production of hydrogen and carbon monoxide, and the gasmixture so produced may be used as such since both components areeiective reducing. agents.

The nature of the present invention will be more readily apparent fromthe following detailed description of the accompanying drawing in whichthe single gure is a front elevation in diagrammatic form of anapparatus suitable for the practice of the present invention.

Referring to the drawing in detail, numeral I designates a tower at thebottom of which is arranged a grate 2 beneath which is a manifold 3connected with a pipe line 4 for the introduction of' reducing andheating gas. The upper end of chamber I is preferably curved to anoutlet which discharges into a separator 5 at the upper end of which isa gas outlet G. The

-lower end of the separator 5 is connected with a second tower 1 whichis of smaller diameter than tower I. At an intermediate point in thistower is arranged an inletI 8 for finely divided iron ore. It will beunderstood that this inlet will in practice take the form of a hopperadapted to discharge powdered ore intermittently into the tower and atother times will be separated in a gas-tight manner from the tower. Thelower end of tower 1 is also preferably curved somewhat in the mannershown so as to connect -with the lower end of tower I. A branch passage9 is connected to the lower end of tower 1 and at the bottom of theintersection Vof the two there is arranged a ap I0, pivoted as shown,arid adapted to deect the stream of powdered iron ore either into thebottom of tower I or into the line 9.

In operation the powdered ore is charged into tower 1 through line 8 anda stream of gas is started in from the manifold 3. The charging of theore is continued while the gas stream is flowing until both tower l andtower 1 are filled with a fairly dense suspension of powdered iron orein gas. The gasvelocity is so regulated as to prevent settling Justabove the grate and keep the stream of iron ore moving at a slow rate.The ore from tower 1 feeds continuously into tower I because it is amuch denser suspension of iron ore, most of the gas having been take offat the top of separator 5. It will be understood that separator 5 issubstantially completely filled with the iron ore suspension, so thatthe whole circulating system is in effect a circulating stream of ironore.

The gas/ admitted., as previously indicated, is of a reducing nature andis preferably hydrogen. Suiiicient air is admitted with the hydrogen toproduce by combustion of the latter suflicient heat to maintain thedesired temperature which will be in the neighborhood of 700 C., and incirculated through the system for a sulcient period of time to becomecompletely reduced, the ap lil is moved so as to deflect the particlesof iron into the discharge line 9.

The powdered product can be wididrawn through line 9 for any usedesired. Where the oxide used is of high purity, the resulting iron powmder will be correspondingly pure and may be used directly for manypurposes without melting. The drawing also illustrates diagrammaticallymeans for melting this powder, to be used as desired.

Line t is provided with a branch line ll in which is a worm conveyor i2.Through this branch line carbon is introduced into the stream of reducediron. This carbon, according to the present invention, is thethermatomic carbon resulting from the pyrolysis of a hydrocarbon gas,

such as methane, used to produce the hydrogen used in the first stage.Also at this point slag forming'materials may be introduced if desiredor if the iron contains ingredients which require their use.

Just behind the junction oi branch line ll, a

worm conveyor i3 is arranged in line 9 which forces the iron and carbon,together with any slag forming constituents, into a vessel Mi where themixture is heated up by the combustion of gas introduced through line l5to a temperature between 11.00 and 160()Q C. The Worm discharge end i3is preferably shielded from the radiant heat oi the\melting zone andcooled by any suitable meansto avoid heating the iron powder to theplastic stage before it is discharged from the worin. It is to be notedthat the gas used is a hydrocarbon gas mixed with sufllcient air oroxygen to give the desired temperature but insuflcient to change thepredominantly reducing nature of the gas.

in vessel ii the iron and carbon combine to n iorrn a low melting alloy(pig iron) which settles assaveo ments of which will be apparent tothose skilled cause the temperature in the reduction zone is maintainedbelow the melting point of iron-carbon alloy. lt is contemplated,according to the present invention, that the carbon resulting from.pyrolysis of methane, for example, will be carried along with thehydrogen into the reduction zone and there mixed with the reduced ironas it is formed. This procedure may be followed without any substantialloss of control over the ironcarbon ratio by continuously sampling theincoming reducing gas, determining its carbon conm tent and controllingsaid content by using a car= bon separator between the pyrolysis zoneand the reduction zone. The procedure illustrated in the drawing,however, permits easier control.

In the above description, it has been stated that sufilcient air isintroduced with hydrogen into manifold il to maintain the desiredtemperature by combustion of the hydrogen. One of the acl-- vantages ofthe present invention is that the hydrogen, when recovered from thepyrolysis of methane, for example, is ata temperature above i00l0 C.,whereby the use ci additional air may be largely or even completelyavoided, In some cases it is more desirable to add the air at a point inthe art. For example, the invention is not limited to the treatment ofiron ore, but is applicable to the recovery of metal from any reduciblecompound thereof. The principle of operation ac cording to which aclosed cycle of moving powdered material to be treated is establishedand the treating uid, ordinarily gas, is used as the motivating powerfor the movement of material around the cycle has general application.It is particularly applicable to any reaction betwee a solid landa gas.

The nature and objects of the present invenn tion having been thusdescribed and illustrated, what is claimed as new and useful and isdesired to be secured by Letters Patent is:

i. In the production of a metal from a finely divided reducible compoundthereof, the steps of ksuspending said compound in a vertically risingstream of a reducing gas confined within a zone maintained at areduction temperature below that at which the metal becomes plastic,maintaining a sufficient vertical gas velocity to prevent settling atthe bottom of said zone and to cause the compound to move slowlyupwardly through out substantially the entire cross section of said @onewith said stream but at lower vglocity, in a dispersion havingcharacteristics of a boiling liquid with respect to mass continuity andsurface disturbance, and discharging the compound reduced at least inpart from an upper part of said zone.

2. Method according to claim. l, in which iinely divided iron ore isreduced.

3. In the production of iron from iron ore, the steps of establishing anupwardly moving stream oi reducing gas in a confined space, maintainingin said space a temperature below that at which iron becomes plastic,feeding into the bottom of said space iron ore ,in sufficiently iinelydivided `form to be capable of being carried along by said stream oigas, removing the finely divided material from the gas at the upper endof said space. and recycling said finely divided material through l apath separated from said space to the lower end of said space.

4. ln the production of iron from iron ore, the steps of establishing aclosed cycle including two substantially vertically arranged passagescona nected'to each other at their ends, introducing finely divided ironore into said cycle,rmoving said iron ore upwardly through one of saidpassages by suspending it in an upwardly moving 'stream of reducing gasmoving at a sulicient ven locity to carry said iron ore, maintaining atleast a portion of said stream at a reducing tempera.- ture below thatat which iron becomes plastic, separating said gas from said iron ore atthe upn per end of said passage, and causing said iron ore to movedownwardly through the other passage by gravity and thence back to theiirst passage.

5. In the production of iron from iron ore, the steps of circulating anely divided ironore in a closed cycle including a zone maintained at areducing temperature below that at which iron becomes plastic,separately decomposing a hydrocarbon gas into therrnatomic carbon andhydrogen, introducing the hydrogen while still at least at thetemperature of the hydrocarbon decomposition into said reducing zone,continuing the cirsedation of the iron ore in said cycle until it issubstantially reduced, discharging the reduced ore from said cycle,mixing it with the thermatomic carbon in proportions suitable for theformation of a low-melting iron-carbon alloy, subjecting the mixture toa temperature at which said alloy is molten, and removing the moltenalloy from the system.

6. In the production of a metal from a metal compound thereof which isreducible at a temperature below the melting point of the metal, thesteps of establishing a closed cycle through which said metal compoundin finely divided form is circulated, said cycle including a verticalreduction zone, maintaining said reduction Vzone at a temperaturesuitable for the reduction of the metal compound below the melting pointof the solid is circulated, one of said towers being substantiallylarger cross-sectional area than the other, means for introducing gas atthe lower end of said tower of larger cross-section, an outlet `for-gasaft'fthe upper end of said towers, means or sage and causing it to passupwardly4 through metal, introducing a reducing gas into said cyclebelow said zone, causing said gas to rise upwardly through said zone ata rate suiiicient to cause/- the metal compound to move upwardlytherethrough in a substantially uniform dispersion in the stream of gasand removing gas and the compound reduced at least in part from saidcycle above said zone.

7. In the production of a metal from a metal compound thereof which isreducible below the melting point of the metal, the steps ofestablishing a closed cycle including two substantially verticallyarranged passages connected to each other at their ends, introducingsaidmetal compound in finely divided form into said cycle, moving saidmetal compound upwardly through one of said passages by suspending it ina stream of reducing gas moving upwardly at a sumcient velocity to carrysaid metal compound, maintaining at least a portion of said stream at areduc-I ing temperature below that at which the metal melts, separatingsaid gas from the finely divided solid at the upper end oi said passage,and causing said finely divided solid to move downwardly through theother passage by gravity and thence baci: to the rst passage.

8. An apparatus suitable for a chemical reaction between a gas and afinely divided solid, comprising a pair of substantially upright towersinterconnected at both their ends to provide a closed cycle throughwhich said iinely divided said passage at a sulcent velocity to preventset- .tling at the bottom of said zone and to cause the solid materialto move slowly upwardly in a substantially uniform dispersion in therising stream of 'gasf maintaining said passage at a reducingtemperature below that at which said metal melts, withdrawing asuspension of reduced metal particles in gas from the upper portion ofsaid passage and separating said reduced metal from the suspending gas.

10. In the production of iron from an orethereof which is reducible tothe metal at a temperature below the melting point thereof, the steps ofproviding a vertically arranged passage, supplying said iron ore iniinely divided form to the lower portion of said passage, supplying areducing gas to the bottom of said passage and causing it to passupwardly through said passage at a suiiicient velocity to preventsettling at the bottom of said zone and'to cause the ore to move slowlyupwardly in a substantially uniform dispersion in the'strearn of gas,said dispersion having characteristics of a boiling liquid with respectto mass continuity and surface disturbance, maintaining said passage ata reducing temperature below the melting point of iron, withdrawing asuspension of reduced iron particles in gas from the upper portion ofsaid passage and separating said reduced iron from the suspending gas.

WARREN K. LEWIS.

